Variation in seven female morphological characters were examined for 18 populations of spider mites of the Tetranychus urticae and T. cinnabarinus complex from greenhouse tomatoes in various locations in the UK. Tetranychus cinnabarinus could be readily separated from T. urticae by variation in the number of setae on tibia I (10–13 setae, or addition of 1–3 solenidia normally present in males) in females and this difference was correlated with those of previously studied characters (shape of dorsal lobe in female and shape of aedeagus in male) and additional characters examined in this paper. Several populations of mites identified as T. cinnabarinus in this study were green in colour. Hyper-necrotic responses in tomato plants were present in most T. cinnabarinus populations with variation in the number of setae on tibia I but absent in T. cinnabarinus population without variation in the number of setae on tibia I (i.e. 13 setae).